add layered bump effect at the root of the a shading tree?

Echo to a similar question posted here. In Arnold 4, I can dial in bump effect in a separate sub-tree and pipe the bump effect in at the root by having the "Bump Map" piped in overall bump effect and the "Shader" slot piped in diffuse, spec, roughness, etc. How can I achieve the same thing in Arnold 5? Basically, in Arnold 4, I have the liberty to decouple the bump shading tree from the main shading tree when layering multiple aiStandard shaders, and "add" the bump at the end at the root. Can we do the same in Arnold 5?